For obtaining the required information about the properties of an environment when creating models, at present arrangements often comprising two or more cameras, for example video cameras or similar, for picture recording of the environment, are used.
One example of the state of the art is the using of so-called stereo cameras. Preferably, two mechanically fixedly connected cameras are used, which have carefully measured or, by exposures of common objects, calculated mutual positions and orientations, With such an arrangement, basic image data may be obtained consisting of large quantities of two-dimensional pictures, most often in pairs, of the environment. However, this basic image data requires considerable processing, including the use of advanced statistical algorithms, which require very heavy calculation power to be able to be transformed to a three-dimensional model of the environment. The fact that several cameras, special mechanics and a lot of calculation work is usually required makes the method costly and time consuming, which in practice means that the standards of quality of the model have to be lowered.
Another method for achieving a three-dimensional model is so-called 3D scanning. In this case the object, which constitutes the basis for the model, is located on a rotating table. Furthermore, the table is suitably vertically adjustable in relation to a scanner located at a distance from the object. By performing repeated measurements of the distance between the scanner and the object by means of the scanner while simultaneously rotating the table, and possibly moving the table vertically, distance information as a function of rotated angle of the table, and the current elevation of the object, is obtained. This distance information may then be used for creating a model of the object. This method however, has great limitations since it is suitable only for producing models of proportionally small objects having elementary shapes. Another weakness is that the object and the scanner are not able to be moved freely in relation to each other during the measuring procedure. It would be desirable to perform measurements from arbitrary positions and in arbitrary directions for obtaining detailed information about the characteristics of the object in the most efficient way.
A further technique for achieving a description of an environment for VR-applications, for instance, is the panoramic technique. It is based on the whole horizon or a great part thereof being photographed from a number of different positions and these pictures being joined together in a computer model. In using the model the viewer can move himself virtually between different positions, the number of which is dependent of the number of picture recording positions which the model was based on. The technique is commercially available and is described for example in U.S. Pat. No. 5,841,440 by Apple Computer Inc and in U.S. Pat. No. 5,684,943 by VPL Research Inc.